Device and method for manufacturing carbonated spring and carbonic water, control method for gas density applied thereto, and membrane module

ABSTRACT

Hot water ( 12 ) in a bath ( 11 ) is pumped up by a suction pump ( 9 ) and introduced into a carbon dioxide gas dissolver ( 7 ) through solution flow rate adjusting means ( 14 ) and then, poured into the bath ( 11 ). Carbon dioxide gas supplied from a carbon dioxide gas cylinder ( 1 ) is introduced into the carbon dioxide gas dissolver ( 7 ) through gas flow rate adjusting means ( 5 ). At this time, the quantity of bubbles existing in artificial carbonated spring in a take-out pipe ( 15 ) is measured with a measuring device ( 13 ), and the solution flow rate adjusting means ( 14 ), gas flow rate adjusting means ( 5 ) and the like are controlled by means of a control device ( 16 ) using a relational expression between a preliminarily set quantity of bubbles and carbon dioxide concentration to obtain a desired concentration of carbon dioxide gas in carbonated spring. Because the carbon dioxide gas flow control means ( 5 ) is provided between the carbon dioxide gas dissolver ( 7 ) and a carbon dioxide gas supply source, carbonated spring of a high concentration can be always manufactured even if the pressure of supplied carbon dioxide gas changes or the permeating performance of a membrane changes.

CROSS-REFERENCED APPLICATIONS

This application is the National Stage of International ApplicationPCT/JP02/08594, filed Aug. 27, 2002, the complete disclosure of which isincorporated herein by reference, which designated the U.S. and thatInternational Application was not published under PCT Article 21(2) inEnglish.

TECHNICAL FIELD

The present invention relates to a device and method for manufacturingcarbonated spring and carbonic water. More specifically, the presentinvention relates to a device and method for manufacturing carbonatedspring and carbonic water having a high concentration in order to alwaysobtain a predetermined carbonic acid concentration effectively. Further,the present invention relates to a method for measuring the gasconcentration of a gas dissolved solution obtained by dissolving gasinto a liquid and a device for manufacturing the solution. Moreparticularly, the present invention relates to a method for controllingthe gas concentration in the solution manufactured continuously to adesired concentration and a device for manufacturing a preferable gasdissolved solution and a membrane module for dissolving gas into theliquid effectively.

BACKGROUND ART

Solution in which gas is dissolved is used for various kinds ofapplication. If exemplifying carbon dioxide gas as a gas, weak carbonicwater having a low carbon dioxide gas concentration, carbonic beveragewhose carbon dioxide gas concentration is intensified under a highpressure, artificial carbonated spring in which carbon dioxide gas isdissolved in hot water, carbon dioxide dissolved solution used forindustrial purpose and the like have been widely used.

Generally, hot spring effects such as blood vessel expansion effectgained in taking bath in hot water containing carbon dioxide gas such ascarbonated spring and difficulty of chilling after bath have been wellknown and utilized in public springs and the like using hot spring sincebefore. The keeping warm effect of the carbonated spring is, basically,considered to be because the physical environment is improved by distalblood vessel expansion effect of contained carbon dioxide gas. Further,carbon dioxide enters the skin so that capillary beds are increased andexpanded thereby improving circulation of blood in the skin. Thus, it isconsidered that this has an effect in cure on regressive disease anddistal circulation trouble. Further, a curative effect under a highconcentration of about several hundreds mg/l to 1,000 mg/l has beenverified in recent years. For the reasons, chemicals and devices capableof providing carbonic water for bath easily have been marketed.

To obtain such carbonated spring artificially, a chemical method forallowing carbonate to react with acid, a method by using combustion gasfrom a boiler, a device for blowing carbon dioxide gas directly into apipe having a throttle as disclosed in Japanese Patent ApplicationLaid-Open NO. 5-238928, a method by using a static mixer as a carbon gasdissolver as disclosed in Japanese Patent Application Publication Nos.7-114790 and 7-114791, and the like are available.

Recently, many methods for producing carbonated spring by using amembrane have been proposed. For example, Japanese Patent No. 2,810,694uses a hollow yarn membrane module incorporating plural porous hollowyarn membranes whose both ends are open and further, Japanese PatentNos. 3,048,499 and 3,048,501, Japanese Patent Application Laid-OpenNo.2001-293344 and the like have proposed methods of using a nonporoushollow yarn membrane as a hollow yarn membrane.

As a method for producing carbonated spring using a membrane, aso-called one-pass type in which carbonated spring is produced bypassing raw water through a carbon dioxide gas dissolver having amembrane module once and a so-called circulation type in which hot wateris circulated in a bath through a carbon dioxide gas dissolver using acirculation pump are available.

Meanwhile, the method by using the porous hollow yarn membrane has sucha fear that the membrane turns hydrophilic due to a long term usage sothat water leaks to the gas side to seal the membrane surface, therebyinitial carbon dioxide gas adding ability is eliminated. Contrary tothis, if the nonporous hollow yarn membrane is used, the nonporousmembrane exists between the gas side and the liquid side, so that nowater may leak to the gas side despite a long term usage. However, thereis a fear that because water vapor which is water molecular passes, thepassing water vapor is condensed on the gas side, thereby the condensedwater (drain) seals the membrane surface.

Thus, according to the Japanese Patent Application Laid-Open Nos.7-313855 and 7-328403, a drain release valve is disposed on the gas sideand the valve is opened/closed periodically to discharge drain from thegas side. However, according to this method, the drain release needs tobe carried out frequently for a membrane in which the amount of passingvapor is large and thus, carbon dioxide gas charged on the gas sideneeds to be discharged into the atmosphere, and therefore, the amount ofconsumption of carbon dioxide gas is likely to be increased.

On the other hand, if the carbonated spring is produced according to themethod by using the membrane, there is a disadvantage that the samecarbon concentration cannot be secured each time although the carbonatedspring having a high concentration can be obtained most highlyeffectively. Particularly, if the carbonated spring is produced a numberof times continuously on the same day, a phenomenon that the carbonicacid concentration drops in the initial period of carbon dioxide gaspassage occurs.

According to the above-described methods, although flow rate andpressure are indicated for control of carbon dioxide gas, only the flowrate is controlled under the pressure control using a pressure controlvalve or the like which is used by being directly connected to a gascylinder as indicated in many of the embodiments. Thus, the flow rate ofthe carbon dioxide gas passing through the membrane differs between theinitial period of the passage and its stabilizing period. The reason whythe flow rate of the carbon dioxide gas changes is considered to be thatbecause the membrane is cooler than the water temperature in the initialperiod and the concentration of carbon dioxide gas in the membrane islow, the carbon dioxide is unlikely to pass through the membrane evenunder the same pressure. However, if carbonated spring having someappropriate concentration is produced, there is no any problem at thattime and not so much attention is paid to the accuracy.

However, in case of carbonated spring in the vicinity of a carbondioxide gas saturated concentration at 40° C., which is around 1200mg/l, it has been made evident that in terms of its curative effect, afurther remarkable effect can be expected and there is no way butchanging a though that everything is satisfied if carbonated springhaving an appropriate concentration is produced. Thus, a necessity ofproducing the carbonated spring with a high concentration and excellentreproducibility is generated. On the other hand, the above-mentionedcarbon dioxide gas dissolver has been modified frequently so thatimprovement of carbon dioxide gas dissolving efficiency has been triedgradually. However, a further improvement in the dissolving efficiencyhas been demanded. Particularly in a full-body bathing device which usesa large amount of carbon dioxide gas, the improvement in the dissolvingefficiency is important.

Even a method using pressure control is capable of producing carbonatedspring having a high concentration if an operation method by providingwith an allowance is used, for example, by setting a slightlyexcessively high pressure or increasing the operation time in case of acirculation type. However, if such a method is applied, carbon dioxidegas is consumed wastefully, which is not preferable.

Further, in case of application for hospitals, a method of producinghigh-concentration carbonated spring in as short a time as possible hasbeen demanded in order to care as many patients as possible. However,the circulation type has such a disadvantage that the time for producingthe high-concentration carbonated spring is prolonged because nosufficient flow rate is secured in the initial period.

On the other hand, the method for producing carbonated spring with anexcellent reproducibility by using the one-pass type has been describedin Japanese Patent Application Laid-Open No. 10-277121. According tothis method, the concentration of carbon dioxide gas in the producedcarbonated spring is measured and by feeding back the concentration, thequantity of carbon dioxide gas supplied is controlled. For the reason,it takes a long time to reach a target carbon dioxide gas concentration.Further, this method has such a disadvantage that if alkali degree ofraw water changes, no excellent reproduction can be attained.

Examples of the method for measuring the concentration of gas in a gasdissolved solution include a method for measuring the gas concentrationby using a gas concentration measuring device of ion electrode type, amethod for measuring the gas concentration by measuring pH afterpreliminarily measured alkaline degrees are programmed, a method formeasuring the gas concentration electrochemically after the pH value ofa solution is adjusted by adding chemical to the solution, a method formeasuring the gas concentration according to thermal conductivity of gasdischarged by adding chemical to a solution, a method for measuring thegas concentration according to infrared ray absorption ratio of asolution, a method for measuring the gas concentration by detecting thepressure of gas discharged from a solution when ultrasonic wave isapplied thereto (Japanese Patent Application Laid-Open No. 5-296904) andthe like.

However, according to the above-described gas measuring method, sinceits operation is very complicated and upon usage, it takes a largenumber of time and labor, the concentration of gas in a solutionproduced continuously from a dissolver cannot be measured on time.

Hereinafter, artificial carbonated spring will be described as anexample of solution. Generally, the artificial carbonated spring isproduced as artificial carbonated spring by dissolving carbon dioxidegas of a predetermined concentration in hot water. Because it isconsidered that the artificial carbonated spring has an excellent effectupon distal blood circulation trouble by its strong blood vesselexpanding action, it has been widely used for cure and hot spring cure.Although carbonated spring spouted naturally is used up to now,currently, the artificial carbonated spring cure has been widely used asone internal medicine cure due to development of the excellentartificial spring production method.

From the clinical research result in the artificial carbonated springcure, it has been made evident that the effective concentration ofcarbon dioxide gas usable for cure becomes max from 1,000 mg/l to about1,400 mg/l. Additionally, it has been indicated that responsibility tothe carbon dioxide gas concentration differs depending on the degree ofseriousness of disease and continuation period of cure. In actualartificial carbonated spring cure, it is necessary to set an appropriateconcentration of carbon dioxide gas corresponding to a patient.

Thus, if the artificial carbonated spring is used for cure, theconcentration of carbon dioxide gas dissolved in a solution is animportant factor. The artificial carbonated spring of a predeterminedconcentration produced continuously with a dissolver requests to takebath just after it is stored in a storage bath. If it takes long formeasurement of the concentration of gas in the artificial carbonatedspring, carbon dioxide gas in the storage bath is emitted into theatmosphere so that the concentration of gas in the artificial carbonatedspring drops. If a patient takes a bath in this condition, he/she cannottake bath under a desired carbon dioxide gas concentration so that thecurative effect by the artificial carbonated spring cannot be expected.Further, when necessity of measuring the gas concentration a number oftimes repeatedly exists, it comes that the temperature of hot wateritself drops.

Particularly, if the carbon dioxide gas concentration is measuredaccording to the ion electrode type method, it takes several minutesuntil a measuring result is obtained, so that the measuring resultcannot be obtained in a short time because several minutes is alwaysneeded for each measurement. Further, according to the method ofmeasuring the carbon dioxide gas concentration by measuring pH after thealkaline degree is programmed preliminarily, it is necessary to measurean alkaline degree preliminarily in each case, the alkaline degreedifferent depending on water quality. Moreover, if other ion or salt ismixed, the alkaline degree needs to be measured again, and to obtain aresponse result of the pH measurement, it takes some time. Thus, thecarbon dioxide gas concentration cannot be measured in line at the sametime when the artificial carbonated spring is produced.

On the other hand, examples of the method for producing the artificialspring include a method of dissolving bubbles of carbon dioxide gasgenerated by chemical reaction in hot water (Japanese Patent ApplicationLaid-Open No. 2-270158), a method of filling hot water in a pressuretank with carbon dioxide gas under a high pressure, a method of mixingcarbon dioxide gas with hot water forcibly by an agitator called staticmixer in a diffuser provided halfway of a hot water conduit (JapanesePatent Application Laid-Open No. 63-242257), a method by using amulti-layer composite hollow yarn membrane dissolver (“Carbonic WaterProducing Device MRE-SPA” made by Mitsubishi Rayon Engineering Co.,Ltd.), and the like.

The methods by using the static mixer or multi-layer composite hollowyarn membrane dissolver are suitable for production of a large amount ofthe artificial carbonated spring continuously and by passing hot waterthrough the carbon dioxide gas dissolver repeatedly by means of thecirculation path, the concentration of the carbon gas can be raisedgradually up to a predetermined concentration.

In case of producing artificial carbonated spring continuously,artificial carbonated spring having a predetermined carbon dioxide gasconcentration can be produced by combining the carbon dioxide gasconcentration measuring means with the artificial carbonated springmanufacturing method. However, the case of producing the artificialcarbonated spring continuously in line has a problem in responsevelocity in the method for measuring the concentration of carbonatedoxide gas. Although measurement based on the ion electrode method is ageneral method as a method for measuring the concentration of carbondioxide gas in water, its response velocity is slow and particularly, asolution whose carbon gas dioxide concentration is 1000 to 1400 mg/l,required for the artificial carbonated spring takes long hours for theion electrode to be balanced. Further, because gas bubbles adhere to theion electrode thereby disabling accurate measurement, the measurement inline and on time is difficult to achieve.

Further, if the membrane is stained gradually each time of use, carbondioxide gas becomes hard to flow, so that a deflection occurs in therelation between a carbon dioxide gas pressure and a flow rate createdfirst, thereby disabling a right flow control. Although it may bepossible to achieve the right control if the relation between pressureand flow rate is investigated each time of use, the operation for thatpurpose is very troublesome.

An object of the present invention is to solve the above-describedproblems and more particularly to provide a device and method formanufacturing carbonated spring and carbonic water having a highconcentration effectively, and a device and method for manufacturingcarbonated spring and carbonic water capable of always obtaining aconstant carbonic acid concentration despite changes in the membranepermeating performance. Another object of the present invention is toprovide a membrane module which allows soluble gas to be dissolved intoliquid effectively, a method for measuring the concentration of gasdissolved in a solution produced continuously in line and on time, and adevice for manufacturing a dissolved solution having a desired gasconcentration effectively.

DISCLOSURE OF THE INVENTION

The most basic configuration of the present invention is a device formanufacturing carbonated spring, comprising: a membrane module whichdissolves carbon dioxide gas into hot water through a membrane; meansfor supplying hot water to the membrane module; and means for supplyingcarbon dioxide gas to the membrane module, wherein a flow control valvewhich maintains the flow rate of carbon dioxide gas constant is providedbetween the means for supplying carbon dioxide gas and the membranemodule.

Preferably, the flow control valve is a mass-flow-rate type flow controlvalve, a flow meter is provided between the flow control valve and themeans for supplying carbon dioxide gas and further, a pressure controlvalve for maintaining gas pressure constant is provided between themeans for supplying carbon dioxide gas and the flow control valve.Adopting such configurations enables the flow rate of carbon dioxide gasto be adjusted more accurately.

Further, preferably, the membrane is hollow yarn and the hollow yarnmembrane is a three-layered composite hollow yarn membrane in which bothsides of a thin nonporous gas permeating layer are sandwiched by porouslayers. If adopting the composite hollow yarn membrane, carbon dioxidegas can be dissolved into hot water or water efficiently.

In addition, the second basic configuration of the present invention isa method for manufacturing carbonated spring, wherein, when carbonatedspring is manufactured by dissolving carbon dioxide gas into hot waterthrough a membrane, the flow rate of carbon dioxide gas is controlled tobe constant. Preferably, as described previously, the carbon dioxide gasflow rate is controlled to be constant by the flow control valve.Preferably, the mass flow rate type flow control valve, a hollow yarnmembrane as the membrane and particularly, a three-layered compositehollow yarn membrane in which both sides of a thin nonporous gaspermeating layer are sandwiched by porous layers are used. Further, whencarbonated spring is manufactured using the circulation type system, theratio between the flow rate of a circulation pump and the flow rate ofcarbon dioxide gas is preferred to be in a range of 2 to 20.

Other basic configuration of the present invention is a device formanufacturing carbonated spring comprising: a carbon dioxide gas supplyport; a carbon dioxide gas dissolver which communicates with the carbondioxide gas supply port; a water bath; a circulation pump for feedingwater in the water bath into the carbon dioxide gas dissolver andreturning the fed water into the water bath; and carbon dioxide gassupply control means for changing the carbon dioxide gas supply velocityduring dissolving of carbon dioxide gas. Still other basic configurationof the present invention is a method for manufacturing carbonatedspring, wherein, when water in a water bath is circulated by acirculation pump through a carbon dioxide gas dissolver while carbondioxide gas is supplied into the carbon dioxide gas dissolver so as todissolve carbon dioxide gas into the water bath to raise the carbondioxide gas concentration of water in the water bath gradually, thecarbon dioxide gas supply velocity is retarded in the latter half periodof the carbon dioxide gas dissolving time as compared with the formerhalf period thereof. According to this manufacturing method, the carbondioxide gas concentration of water in the water bath after dissolving ofcarbon dioxide gas ends is preferred to be 1000 mg/l or more. By settingthe carbon dioxide gas concentration to a high concentration, bloodcirculation in the skin becomes easy to improve due to distal bloodvessel expansion action by the contained carbon dioxide gas andincrease/expansion of capillary beds by invasion of carbon dioxide gasthrough the skin.

Still other configuration of the present invention is a device formanufacturing a gas dissolved solution for carbonated spring,comprising: a carbon dioxide gas supply port; a carbon dioxide gasdissolver which communicates with the carbon dioxide gas supply port; awater bath; a circulation pump for feeding water in the water bath intothe carbon dioxide gas dissolver and returning the fed water into thewater bath; and carbon dioxide gas supply control means for changing thecarbon dioxide gas supply velocity during dissolving of carbon dioxidegas.

Preferably, when carbonated spring is manufactured by dissolving carbondioxide gas into hot water through a membrane, the carbon dioxide gasflow rate is controlled to be constant. Preferably, a mass flow ratetype flow control valve is used as the flow control valve, a hollow yarnmembrane is used as the membrane, and particularly, a three-layeredcomposite hollow yarn membrane in which both sides of a thin nonporousgas permeating layer are sandwiched by porous layers is used. Further,the latter half of carbon dioxide gas dissolving time is preferred to belonger than the former half of carbon dioxide gas dissolving time. Thecarbon dioxide gas supply velocity just before dissolving of carbondioxide gas ends is preferred to be 50% or less with respect to thesupply velocity when dissolving of carbon dioxide gas starts.Consequently, carbonated spring having a high concentration can bemanufactured effectively.

In order to control the carbon dioxide gas supply velocity, it ispermissible to provide plural carbon dioxide gas supply velocity controlmeans in parallel. In this case, the carbon dioxide gas supply velocitycontrol means may be set to different supply velocities and then,changed over in order from the carbon dioxide gas supply velocitycontrol means having the highest setting of the carbon dioxide gassupply velocity. To change over the carbon dioxide gas supply velocity,it is desirable to use an electromagnetic valve and change over in orderunder electronic control.

Further, to control the carbon dioxide gas supply velocity, preferably,the flow control valve is used.

As described above, the flow control valve is preferred to be a massflow rate type flow control valve. Preferably, a flow meter is providedbetween the flow control valve and the means for supplying carbondioxide gas and a pressure control valve for maintaining gas pressureconstant is provided between the means for supplying carbon dioxide gasand the flow control valve. With these structures, the flow rate ofcarbon dioxide gas can be adjusted accurately.

Generally, as the flow control valve, there are a type affecting thesecondary pressure (outlet side pressure) such as an ordinary orificeand needle valve and a type not affecting the secondary pressure. Incase of the type affecting the secondary pressure, as the pressure ofthe secondary side increases, that is, a difference to the primarypressure decreases, the flow rate is reduced. At this time, the valveopening degree (CV value) and pressure are generally in a followingrelation.

Assuming that P₁ is a primary side absolute pressure (MPa), P₂ is asecondary side absolute pressure (MPa), Q is a flow rate (m³/h), and ρis a specific weight (assuming air to be 1), when P₂>(P₁/2),CV=Q/4170×(p(273+t)/(P ₁ −P ₂)P ₂)^(1/2)When P₂≦(P₁/2), the secondary pressure is not affected.

On the other hand, the mass flow control valve does not affect thesecondary pressure.

According to Japanese Patent Application Laid-Open NO. 58-139730, whenthe pressure is constant, carbon dioxide gas is fed, that is, becausethe secondary pressure is constant, the mass flow control valve is notrequired.

Contrary to this, preferably the mass flow control valve is adoptedbecause the present invention utilizes the membrane module in which thesecondary pressure changes depending on changes in state. As a wellknown mass flow control valve, there are an electronic valve and needlevalve. Although according to the present invention, the needle valvetype mass flow control valve is preferably used, it is permissible touse the electronic type.

The mass flow control valve of the needle valve type adjusts the flowrate with a needle valve and is provided with a pressure adjusting valveor the like whose opening degree is constant to the same mass flow rateso that the pressure at a valve outlet becomes constant, provided at therear portion thereof. Consequently, the secondary pressure (outletpressure) is always kept constant. Because the secondary pressure turnsconstant when the primary pressure (intake pressure) is constant, thevalve is called constant differential pressure adjusting valve. Althoughthe ordinary needle valve affects the secondary pressure, this mass flowcontrol valve can adjust the mass flow rate to constant even if the loadpressure on the secondary side (outlet side) changes.

On the other hand, in the electronic mass flow control valve, resistorseach having a large resistance temperature coefficient are wound arounda capillary tube which is a sensor portion at its upstream anddownstream sides and by supplying a current to this, the two resistorsare heated. At this time, if no fluid flows through the capillary tube,the upstream and downstream sides are balanced with the sametemperature. If fluid begins to flow in this state, the temperaturedistribution changes, so that the upstream side is deprived of heat byfluid while the downstream side is supplied with heat deprived from theupstream side. That is, there is generated a difference in temperaturebetween the upstream and downstream sides.

If attention is paid to that this temperature difference is in apredetermined functional relationship with the mass flow rate of fluidand a change of each resistance is fetched out as an electric signal andthen, amplified and corrected, a thermal type mass flow rate metercapable of measuring the mass flow rate functions under a certaincondition. This is an electronic type mass flow rate meter (mass flowmeter).

In the mass flow control valve (mass flow controller), a valve openingdegree is controlled by a high-speed, high-resolution piezo or solenoidactuator under comparative control with a flow rate setting signal fromoutside based on a signal of mass flow rate outputted from the sensorportion. Consequently, a stabilized mass flow control is enabled hardlyaffected by changes in various conditions such as temperature andpressure.

According to the present invention, in the gas permeation membranepreferable for carbon dioxide gas, preferably, its carbon dioxide gaspermeating amount at 25° C. is 1×10⁻³ to 1 m³/m²·hr·0.1 MPa and itsvapor permeating amount at 25° C. is 1×10³ g/m²·hr·0.1 MPa or less.Further, it is preferable to use a membrane module composed of these gaspermeation membranes. If the gas permeation membrane is a nonporousmembrane having no Knudsen flow, the membrane gets wet so that no waterpermeates to the gas supply side, which is preferable. If the membranedensity of the membrane module is in a range of 2000 to 7000 m²/m³,carbon dioxide gas can be dissolved effectively, which is preferable.

It is preferable that the gas permeation membrane is a hollow yarnmembrane, because the membrane area per volume can be raised. Althoughthis hollow yarn may be composed of hollow yarn membrane formed of mereporous membrane, if the hollow yarn membrane is a three-layeredcomposite hollow yarn membrane in which both sides of a thin nonporousmembrane are sandwiched by porous membranes, carbon dioxide gas can bedissolved into hot water efficiently, which is preferable. If thethickness of the nonporous membrane is 0.1 to 500 μm, an appropriatestrength is possessed while carbon dioxide gas permeating performanceand vapor permeating performance are satisfied, which is preferable. Todissolve carbon dioxide gas using the carbon dioxide gas adding membranemodule, it is preferable to heat water to 30° C. to 50° C. preliminarilyand then dissolve it. Further, the carbon dioxide gas dissolver may be astatic mixer.

Moreover, to manufacture the above-described high concentrationcarbonated spring or carbonic water of 1000 mg/l or more, the method formeasuring the gas concentration in a dissolved solution which is anotheraspect of the present invention can be adopted. This is a gasconcentration measuring method developed by the inventor of the presentinvention, and applies the fact that when the flow rate of solutionpassing the gas dissolver and the supply flow rate of gas supplied tothe same gas dissolver are kept constant, there exists a certaincorrelation between the quantity of bubbles of undissolved gas existingin the take-out pipe from the gas dissolver and the gas concentration inthe dissolved solution introduced from the gas dissolver. Consequently,the gas concentration in the dissolved solution manufacturedcontinuously can be measured in line and on time. In the meantime, thegas concentration measuring method of the present invention is notrestricted to measurement of the gas concentration in the carbon dioxidegas solution only, but naturally may be applied to measurement of gasconcentration of other various kinds of soluble gases.

The basic configuration exists in a method for measuring a gasconcentration in a dissolved solution, comprising introducing solutionand gas of each specified flow rate into a gas dissolver, measuring thequantity of bubbles existing in a take-out pipe from the gas dissolverand measuring the gas concentration of a dissolved solution dischargedfrom the take-out pipe according to the quantity of the bubbles.

By introducing a specified amount of solution into the gas dissolver anda specified amount of gas, a dissolved solution after gas is dissolvedinto solution in the gas dissolver and gas not dissolved in solution,that is, gas mixed in the dissolved solution in the form of bubbles isdischarged through the take-out pipe from the gas dissolver. Thequantity of bubbles of undissolved gas existing in the take-out pipe ismeasured continuously in line and on time so as to measure the gasconcentration in the dissolved solution introduced out from the gasdissolver continuously. As the quantity of gas introduced into the gasdissolver, it is desirable to introduce a quantity not less than thesaturated dissolved amount of the quantity of the introduced solutioninto the gas dissolver.

When obtaining a dissolved solution having a target gas concentration byadding gas to dissolved solution of any concentration through multiplestages, the quantity of gas which can be added in a next stage isdecreased as the gas concentration of an initial dissolved solution ishigher. Moreover, to maintain the flow rate of solution passing the gasdissolver and the supply flow rate of gas supplied to the same gasdissolver, the quantity of bubbles of undissolved gas existing in thetake-out pipe from the gas dissolver and the gas concentration in thedissolved solution introduced out from the gas dissolver have a specificcorrelation. Using this fact, the gas concentration in the dissolvedsolution can be measured on time during continuous manufacturing of thedissolved solution by measuring the quantity of bubbles in the dissolvedsolution in the take-out pipe according to a relational expression,which indicates the relation between the quantity of bubbles in thedissolved solution existing in the take-out pipe and the gasconcentration of the dissolved solution and is obtained under variousconditions in terms of the dissolving capacity of a gas dissolver, theintroduction amount of solution and the flow rate of introduced gas.

When the dissolved solution is artificial carbonated spring, the gasconcentration of the artificial carbonated spring manufactured by thegas dissolver can be measured continuously in line and on timeeffectively from the quantity of bubbles in the take-out pipe duringmanufacturing of the artificial carbonated spring.

In addition to the above-described configuration, the quantity of thebubbles is preferred to be computed according to the damping rate ofultrasonic wave passing the take-out pipe using an ultrasonic wavetransmitter and an ultrasonic wave receiver disposed across the take-outpipe. As regards measuring of bubbles of gas in the dissolved solution,the quantity of bubbles is computed according to a damping rate(=(strength of ultrasonic wave signal received by ultrasonic wavereceiver)/(strength of ultrasonic wave signal transmitted fromultrasonic wave transmitter): %) of the strength of an ultrasonic wavesignal received by the ultrasonic wave receiver disposed in the take-outpipe after the ultrasonic wave signals dispatched from the ultrasonicwave transmitter disposed in the introduction pipe are passed throughthe dissolved solution in the take-out pipe.

The quantity of bubbles can be measured by causing the ultrasonic wavesignal to pass through the take-out pipe in which the quantity ofbubbles of gas in the dissolved solution and the solution coexist. Thatis, the damping of the ultrasonic wave signal measured by the ultrasonicwave receiver is minimized (the damping rate is maximized) because theultrasonic wave signal dispatched from the ultrasonic wave transmitterpasses only the solution when no gas bubbles exist in the solution (whenthe supply amount of gas is 0 or gas introduced into the gas dissolveris dissolved 100% in the solution because the gas supply velocity to theflow velocity of the solution is small).

Because the conductivity of ultrasonic wave is different betweensolution and bubble, the damping of the ultrasonic wave signal increasesas more bubbles are mixed in the solution and when the solubility in thegas dissolver for use reaches 0, the damping of the ultrasonic wavesignal measured by the ultrasonic wave receiver is maximized (thedamping rate is minimized). Because the change in the damping rate ofthe ultrasonic wave signal is inherent of a gas dissolver, it ispossible to obtain a relational expression to a gas dissolver for use bymeasuring the damping rate of the ultrasonic wave signal and a measuredvalue of the gas concentration in the solution.

Particularly, because when the artificial carbonated spring is adoptedas the solution, there is a tendency that the damping rate decreasesrapidly from the saturated concentration of carbon dioxide gas in theartificial carbonated spring, the change in the damping rate is large inthe vicinity of 1000 to 1400 mg/l which is an effective carbon dioxidegas concentration as the artificial carbonated spring, so that thecarbon dioxide gas concentration in the effective carbon dioxide gasconcentration range can be measured easily according to the quantity ofbubbles.

According to the present invention, preferably, the gas concentration isspecified according to the quantity of the measured quantity of bubblesusing the relational expression between the quantity of bubbles and gasconcentration measured under a condition that the solution flow rate andgas flow rate are constant. Here, the inventor of the present inventionhas recognized first that there exists a specified correlation betweenthe quantity of bubbles in undissolved gas existing in the take-out pipefrom the gas dissolver and the gas concentration in the dissolvedsolution taken out from the gas dissolver or taken into the gasdissolver by maintaining the flow rate of solution passing the gasdissolver and the supply amount of gas supplied to the same gasdissolver and this recognition is applied to the present invention.

That is, this specification can be carried out according to therelational expression by measuring the damping rate of the ultrasonicwave signal and the measured value of the gas concentration for thestate of solution to be introduced to the gas dissolver and the state ofgas. The states of the solution and gas can be set up depending onphysical condition (for example, flow rate for introduction, pressure,temperature, viscosity and the like). Because the relational expressionbetween the damping rate of the ultrasonic wave signal and the measuredvalue of the gas concentration differs depending on the physicalconditions of the solution and gas, it is desirable to keep the aboverelational expression under a condition for carrying out normaldissolving work.

Because the above-described relational expression differs depending onthe dissolving capacity of the gas dissolver, the temperature, pressureand the like at the time of dissolving, it is necessary to set up theseconditions depending on the condition for actually manufacturing thedissolved solution to obtain the above relational expression based onthe same condition.

Particularly, in case where the artificial carbonated spring is employedas the dissolved solution, it is desirable to obtain the aforementionedrelational expression under the condition that the introduction flowrates of the artificial carbonated spring or hot water and theintroduction flow rate of carbon dioxide gas are kept at a desired flowrate at a temperature suitable for taking bath as the temperature of hotwater of artificial carbonated spring. The gas concentration measuringmethod of the present invention is capable of obtaining a preferableresult if the gas dissolved solution is artificial carbonated spring. Inmanufacturing, for example, artificial carbonated spring using carbondioxide gas as its gas, the gas concentration in the artificialcarbonated spring being manufactured is measured based on the quantityof bubbles of carbon dioxide gas in the take-out pipe discharged fromthe gas dissolver.

Thus, the gas concentration of the artificial carbonated springmanufactured by the gas dissolver can be measured continuously on timeeffectively according to the quantity of bubbles in the take-out pipeduring manufacturing of the artificial carbonated spring. Further, bymaking the bast of a tendency that the damping rate of the ultrasonicwave signal decreases rapidly from the vicinity of the saturatedconcentration of the carbon dioxide gas of the artificial carbonatedspring, the carbon dioxide gas concentration in the vicinity of 1000 to1400 mg/l, which is an effective carbon dioxide gas concentration as theartificial carbonated spring, can be detected or measured easily.

At a temperature suitable for taking bath in the artificial carbonatedspring, an relational expression between the quantity of bubbles ofcarbon dioxide gas in the artificial carbonated spring taken out fromthe gas dissolver and the gas concentration of the artificial carbonatedspring is obtained preliminarily with the flow rate of the artificialcarbonated spring or hot water introduced into the gas dissolver and theintroduction flow rate of carbon dioxide gas set to desired specificflow rates. Then, the carbon dioxide gas concentration of the artificialcarbonated spring can be obtained in line and on time duringmanufacturing of the artificial carbonated spring.

According to still another aspect of the present invention, the gasconcentration measuring method is achieved by a device for manufacturinga gas dissolved solution, comprising: a gas supply source having gasflow rate adjusting means; a gas dissolver in which gas and solution areto be introduced from the gas supply source; solution flow rateadjusting means for controlling the flow rate of the solution introducedinto the gas dissolver to be constant; and a take-out pipe for takingout the solution from the gas dissolver, the manufacturing devicefurther comprising: a measuring device for measuring the quantity of gasbubbles existing in the take-out pipe; and a control device forcomputing the gas concentration of the dissolved solution based on arelational expression between the quantity of bubbles and gasconcentration measured preliminarily under a condition that the solutionflow rate and gas flow rate are constant and a measured value from themeasuring device and controlling the gas flow rate adjusting meansand/or the solution flow rate adjusting means based on the computationresult, securely and accurately.

According to the present invention, the gas concentration of a dissolvedsolution is computed according to the quantity of gas bubbles existingin the take-out pipe under measurement using the relational expressionbetween the quantity of bubbles and gas concentration obtained bypreliminary measurement. Then, a dissolved solution having a desired gasconcentration can be manufactured by controlling the gas flow rateadjusting means and/or the solution flow rate adjusting means dependingon the computed gas concentration of the dissolved solution.

As regards control on the gas flow rate adjusting means and/or thesolution flow rate adjusting means, the introduction from the gas flowrate adjusting means and solution flow rate adjusting means into the gasdissolver can be stopped when the gas concentration of the dissolvedsolution computed by the control device reaches a desired gasconcentration. Further, the gas concentration in the dissolved solutioncan be controlled based on the relational expression at changed flowrates in the gas flow and solution flow.

In this case, a number of the relational expressions between the gasflow rate and solution flow rate, which can be changed over in advance,are prepared preliminarily and then, the gas flow rate and solution flowrate optimum for a desired gas concentration are computed from the gasconcentration computed from the quantity of bubbles in the solution.Then, the gas flow rate adjusting means and solution flow rate adjustingmeans are controlled so as to reach the gas flow rate and solution flowrate on the relational expression which is preliminarily measured and isthe nearest the above computation result.

The measuring device is preferred to be composed of the ultrasonic wavetransmitter and ultrasonic wave receiver disposed across the take-outpipe. By using the gas dissolved solution manufacturing device havingsuch a configuration, the above-described operation and effect can beobtained.

The gas dissolver may be constituted of a static mixer. Because thestatic mixer is a gas dissolver capable of introducing a specific amountof solution and soluble gas continuously from viewpoint of its structureand has a relatively high dissolving efficiency, it is advantageous toadopt this as a dissolver. Particularly, because the static mixer is agas dissolver capable of introducing a specified amount of hot water andcarbon dioxide gas continuously and easily upon manufacturing of theartificial carbonated spring and has a high dissolving efficiency forcarbon dioxide gas, it is advantageous as a gas dissolver formanufacturing the artificial carbonated spring.

Preferably, the gas dissolver is a hollow yarn membrane type dissolver.The hollow yarn membrane type dissolver allows gas to be dissolved insolution to be supplied at a stable flow rate and secures a highdissolving efficiency, so that gas can be dissolved in solution in awider concentration range.

In the hollow yarn membrane type dissolver, solution is passed on acontact portion on the surface of the hollow yarn membrane and throughone side of the hollow portion while gas is passed through the otherside, so that gas is dissolved in solution using the action as a gasexchange membrane in the hollow yarn membrane. At the time of dissolvinggas, it is preferable to adjust the gas pressure and solution pressureto a pressure capable of obtaining a dissolved solution not less thanthe saturated gas concentration by adjusting the gas pressure adjustingunit and solution pressure adjusting unit connected to the hollow yarnmembrane type dissolver.

Particularly, its dissolving efficiency is relatively high in aconcentration region of 1000 mg/l or more necessary for the artificialcarbonated spring for manufacturing of the artificial carbonated spring,the relational expression between the quantity of bubbles and the carbondioxide gas concentration is maintained excellently and it is capable ofdetecting the carbon dioxide gas concentration in a carbon dioxide gasconcentration region effective for the artificial carbonated spring at ahigh accuracy.

Preferably, it further comprises a storage bath for storing dissolvedsolution discharged from the take-out pipe, wherein liquid in thestorage bath is circulated to the gas dissolver through the solutionflow rate adjusting means. A desired amount of gas can be dissolved inthe dissolved solution from the gas dissolver by circulating thesolution in the storage bath through the solution flow rate adjustingmeans. Thus, the dissolved solution in the storage bath is introducedfrom the storage bath into the gas dissolver through a liquid feedingpump or the like and gas is added gradually to the dissolved solution soas to raise the gas concentration.

By measuring the gas concentration of the dissolved solution passing thegas dissolver, gas can be added until the gas concentration of thedissolve solution in the storage bath reaches a target gasconcentration, so that a dissolved solution of a desired gasconcentration can be manufactured. At this time, if a relationalexpression between the damping rate of the ultrasonic wave signal andthe gas concentration of the solution introduced into the dissolverinstead of the gas concentration of the solution taken out from thedissolver is obtained preliminarily for a gas dissolver for use, the gasconcentration of the solution in the storage bath can be detected.

Even if new solution is added to the storage bath, a dissolved solutionof a desired gas concentration can be manufactured by circulating thedissolved solution into the gas dissolver. Thus, a dissolved solution ofa desired gas concentration can be always held at a specified amount inthe storage bath.

On the other hand, a target gas concentration can be manufacturedcontinuously by changing the ratio between the flow rate of solution tobe introduced into the gas dissolver and the gas supply flow rate whilemeasuring the gas concentration in the dissolved solution which passesthrough the gas dissolver, the solution being introduced directly intothe storage bath through a supply port such a faucet.

Upon manufacturing of the artificial carbonated spring, the artificialcarbonated spring having a desired carbon dioxide gas concentration canbe manufactured easily by circulating the artificial carbonated springto the gas dissolver and further a desired amount of the artificialcarbonated spring can be manufactured continuously while measuring thecarbon dioxide gas concentration.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a schematic entire configuration of acirculation type device preferably used for the present invention;

FIG. 2 is a diagram showing a schematic entire configuration of anothercirculation type device preferably used for the present invention;

FIG. 3 is a diagram showing a schematic entire configuration of aone-pass type device preferably used for the present invention;

FIG. 4 is a schematic sectional view showing an example of a carbondioxide gas adding membrane module of the present invention;

FIG. 5 is a schematic view showing an example of a hollow yarn membranefor use in the present invention;

FIG. 6 is a diagram showing a configuration of a device formanufacturing artificial carbonated spring according to an embodiment ofthe present invention;

FIG. 7 is a relational diagram between damping rate and gasconcentration; and

FIG. 8 is a block diagram of signal processing.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 shows a device of circulation type for manufacturing carbonatedspring as an example of a diagram schematically showing an entireconfiguration of a preferable device of the present invention. Referencenumeral 1 denotes a carbon dioxide gas cylinder, reference numeral 2denotes a pressure gauge, reference numeral 3 denotes a pressure controlvalve, reference numeral 4 denotes a flow meter, reference numeral 5denotes a flow control valve, reference numeral 6 denotes a carbondioxide gas introduction intake, reference numeral 7 denotes a carbondioxide gas dissolver, reference numeral 8 denotes a hot waterintroduction intake, reference numeral 9 denotes a circulation typesuction pump, reference numeral 10 denotes a carbonated spring dischargeport, reference numeral 11 denotes a bath and reference numeral 12denotes hot water.

FIG. 2 is a diagram schematically showing an entire configuration ofanother preferred device of the present invention. Reference numeral 1denotes a carbon dioxide gas cylinder, reference numeral 2 denotes apressure gauge, reference numeral 3 denotes a pressure control valve,reference numeral 4′ denotes an electromagnetic valve, reference numeral5 denotes a flow control valve, reference numeral 6 denotes a carbondioxide gas introduction intake, reference numeral 7 denotes a carbondioxide gas dissolver, reference numeral 8 denotes a hot waterintroduction intake, reference numeral 9 denotes a circulation typesuction pump, reference numeral 10 denotes a carbonated spring dischargeport, reference numeral 11 denotes a bath, and reference numeral 12denotes hot water.

Water in the bath 11 is circulated by the circulation type suction pump9 through the carbon gas dissolver 7 and carbon dioxide gas is suppliedinto the carbon dioxide gas dissolver. By dissolving carbon dioxide gasinto water (hot water) so as to raise the concentration of carbondioxide gas in water gradually, carbonated spring of an always highpredetermined concentration is produced.

FIG. 3 is a diagram schematically showing an entire configuration ofstill another preferred device of the present invention, indicating aone-pass type carbonated spring producing device. Reference numeral 1denotes a carbon dioxide gas cylinder, reference numeral 2 denotes apressure gauge, reference numeral 3 denotes a pressure control valve,reference numeral 4 denotes a flow meter, reference numeral 5 denotes aflow control valve, reference numeral 6 denotes a carbon dioxide gasintroduction intake, reference numeral 7 denotes a carbon dioxide gasdissolver, reference numeral 8 denotes a hot water introduction port andreference numeral 10 denotes a carbonated spring discharge port.

Carbon dioxide gas is reduced to a predetermined pressure from thecarbon dioxide gas cylinder 1 by the pressure control valve 3 and theflow rate is controlled by the flow control valve 5. After that, it isfed into the carbon dioxide gas dissolver 7 through which hot waterflows so that it is dissolved in the hot water.

Although these devices may be provided with no pressure control valve 3,it is preferable to provide with it for the safety and for control ofthe flow control valve 5, which is provided later. Although the pressurecontrol valve 3 is not restricted to any particular type, an ordinarypressure reduction valve, whish is installed directly on a cylinder, maybe accepted.

Pressure control of carbon dioxide gas applied on the membrane is notrequired and what is important is control on the flow rate of carbondioxide gas flowing on the membrane. If the flow rate of the carbondioxide gas is regulated to constant, pressure applied on the membraneis high in the initial period of gas passage and thereafter, it dropsgradually. The membrane is stained each time when it is used, so thatthe pressure rises gradually, but the pressure of carbon dioxide gasapplied to the membrane does not affect manufacturing of carbonatedspring at a high precision.

Thus, flow control on the carbon dioxide gas flowing on the membrane isvery important. As the flow control valve 3, various kinds of needlevalves, for example, electronically used piezo or solenoid actuator canbe picked up and although not particularly limited, a needle valve ispreferable because it is cheap. Further, it is permissible to use anorifice having a throttle. The function of this flow control valve 5 isimportant for the present invention and particularly, even if thepressure or temperature changes, a mass flow rate type which has thefunction for always keeping the flow rate constant is preferable. Apressure is applied when carbon dioxide gas is fed into the carbon gasdissolver and the pressure differs between in the initial period of gaspassage and at the stabilizing time. Thus, a type having this functioncan perform more stabilized flow control.

Although the flow control valve 5 can always control the flow rate toconstant if its knob is fixed, it is preferable to provide with a flowmeter because the flow meter can be checked visually and judgedinstantly when any trouble occurs. As the flow meter, a float typevolume flow meter and current temperature difference detection type massflow meter can be mentioned and although not limited, the mass flowmeter is more unlikely to be affected by the pressure and temperature.

Regarding the flow rate of carbon dioxide gas, in case of thecirculation type, the flow rate ratio between the flow rate of thecirculation pump and carbon dioxide gas is set to 2 to 20, preferably, 3to 10. Within this range, the dissolving efficiency is raised. If it issmaller than that range, the dissolving efficiency drops remarkably andconversely if it is larger, the dissolving efficiency is excellent butthe flow rate of the circulation pump is increased or the flow rate ofcarbon dioxide gas is decreased. Thus, consumption power is consumedwastefully or the production time is prolonged, which is not preferable.In case of one-pass type, the flow rate of carbon dioxide gas per unitmembrane area is set to be in a constant range.

As the carbon gas dissolver, a membrane module can be used.

Although as the configuration of the membrane in the carbon gasdissolver, flat membrane, tubular membrane, hollow yarn membrane, spiralmembrane and the like can be mentioned, the hollow yarn membrane is mostpreferable in terms of compactness of the device and ease of handling.

Various kinds of membranes may be used as long as they have an excellentgas permeability, and both porous hollow yarn membrane and nonporoushollow yarn membrane are acceptable. If the porous hollow yarn membraneis used, the diameter of an opening hole in its surface is preferred tobe 0.01 to 10 μm. The most preferable hollow yarn membrane is athree-layer composite hollow yarn membrane in which a thin nonporous gaspermeable layer is sandwiched by porous layers on both sides and itsspecific example is, for example, a three-layer composite hollow yarnmembrane (MHT-200TL, product name) made by Mitsubishi Rayon Co., Ltd.

The nonporous gas permeable layer (membrane) is a membrane which gaspasses by a dissolving/diffusion mechanism to its membrane substrate andany membrane is acceptable if molecules substantially do not containholes which gas can pass in a gas form like Knudsen flow. If thenonporous substance is used, the gas can be supplied and dissolvedwithout being emitted into carbonated spring as bubbles under any flowrate thereof and further dissolved effectively and controlled to anyconcentration because it can be dissolved easily. Although in case ofthe porous membrane, hot water sometimes backflows to the gas supplyside through pores, in case of the nonporous membrane, no hot waterbackflows to the gas supply side through the pores. In the three-layercomposite hollow yarn membrane, its nonporous layer is formed verythinly to have an excellent gas permeability and protected by poroussubstance so that it is hard to damage.

The gas permeation membrane is preferred to be of nonporous membraneincluding no Knudsen flow, thereby there being no fear that the membraneturns hydrophilic during a long term usage, causing a water leakage.

As described above, the membrane thickness of the nonporous membrane ispreferred to be in a range of 0.1 μm to 500 μm. If the membranethickness is smaller than 0.1 μm, the membrane production and handlingare difficult. If the membrane thickness is larger than 500 μm, thevapor permeating amount drops while the carbon gas permeating amountdrops also, so that a very large membrane area is required to obtain anecessary performance.

Preferably, the membrane thickness of the hollow yarn membrane is 10 to150 μm. If it is less than 10 μm, membrane strength becomes insufficientand if it exceeds 150 μm, the passing velocity of carbon dioxide gasdrops so that its diffusion efficiency is likely to drop. In case of thethree-layer composite hollow yarn membrane, the thickness of thenonporous membrane is 0.3 to 20 μm. If it is less than 0.3 μm, membranedeterioration is likely to occur and if the membrane is deteriorated,leakage is likely to occur. If the membrane thickness exceeds 20 μm, thepassing velocity of carbon dioxide gas drops, which is not preferable.

Examples of a preferable hollow yarn membrane material include siliconebase, polyolefin base, polyester base, polyamide base, polyimide base,polysulfone base, cellulose base, polyurethane base and the like.Examples of the preferable materials of the nonporous membrane in thethree-layered composite hollow yarn membrane include polyurethane,polyethylene, polypropylene, poly-4-methylpentene-1,polydimethylsiloxane, polyethyl cellulose, polyphenylene oxide and thelike. Particularly, polyurethane has an excellent membrane producingproperty with a small amount of eluted substance.

If the hollow yarn membrane is used for the carbon dioxide gasdissolver, there are a method in which carbon dioxide gas is suppliedinside pores in the hollow yarn membrane and hot water is supplied tothe side of the outer surface so as to dissolve carbon dioxide gas and amethod in which carbon dioxide gas is supplied to the side of the outersurface of the hollow yarn membrane and hot water is supplied insidepores so as to dissolve carbon dioxide gas. If carbon dioxide gas issupplied to the outer surface of the hollow yarn membrane while hotwater is supplied inside the pores so as to dissolve carbon dioxide gas,carbon dioxide gas can be dissolved in hot water at a high concentrationregardless of the configuration of the membrane module.

The inside diameter of the hollow yarn membrane is preferred to be 50 to1000 μm. If it is less than 50 μm, resistance of a flow path to carbondioxide gas or hot water flowing through the hollow yarn membrane isincreased, so that supply of carbon dioxide gas or hot water isdisabled. Further, if it exceeds 1000 μm, the size of the dissolver isincreased, thereby not making it possible to achieve compactnessthereof.

In the carbon dioxide gas dissolver for use in the present invention,the gas diffusing portion composed of porous substance may be providedwith gas diffusing means installed on the bottom portion of the carbondioxide gas dissolver. Although the material and configuration of theporous substance disposed in the gas diffusing portion are notrestricted to any particular ones, porosity, namely, volume ratio to theentire porous substance of pores existing in the porous substance itselfis preferred to be in a range of 5 to 70 vol %. To raise the dissolvingefficiency of carbon dioxide gas, it is better as the porosity is lowerand it is preferred to be 5 to 40 vol %. If the porosity exceeds 70 vol%, it is difficult to control the flow rate of carbon dioxide gas sothat bubbles of carbon dioxide gas diffused from the porous substancebecome huge thereby likely decreasing the diffusing efficiency. If theporosity is less than 5 vol %, the supply amount of carbon dioxide gasdecreases and thus, it tends to take a long time to dissolve carbondioxide gas.

FIG. 4 is a sectional view showing an example of the hollow yarnmembrane module of the present invention. A hollow yarn membrane 21 isfixed to a fixing member 23 within a housing 20 with opening state atboth ends thereof kept and the side in which water flows and the side inwhich carbon dioxide gas is supplied are sealed by the fixing member 23such that no liquid is permitted to enter.

The housing 20 is provided with an intake 24 and an outlet 25communicating with a hollow portion in the hollow yarn membrane 21.Further, it is provided with an intake 26 and an outlet 27 communicatingwith the outer surface of the hollow yarn membrane 21.

As the gas permeation membrane used in the present invention, a membranewhose carbon dioxide gas permeating amount at 25° C. is 1×10⁻³ to 1m³/m²·hr·0.1 MPa is used. If the carbon dioxide gas permeating amount islower than 1×10⁻³ m³/m²·hr·0.1 MPa, carbon dioxide gas cannot bedissolved in water efficiently and if it is higher than 1 m³/m²·hr·0.1MPa, a large amount of carbon dioxide gas permeates under a lowpressure. Thus, even a small deflection in pressure is not preferablebecause the permeating amount changes largely.

Further, the gas permeation membrane for use is a membrane whose vaporpermeating amount at 25° C. is 1×10³g/m²·hr·0.1 MPa or less. If thevapor permeating amount is higher than 1×10³g/m²·hr·0.1 MPa, a necessityof discharging drain out of the membrane module frequently occurs, whichis not preferable.

Furthermore, if the carbon dioxide gas permeating amount is 1×10⁻² to1×10⁻¹ m³/m²·hr·0.1 MPa and the vapor permeating amount is 1×10²g/m²·hr·0.1 MPa or less, it is more preferable.

The vapor permeating amount and carbon dioxide gas permeating amountmentioned here refer to weight of vapor and volume of the carbon gaspermeation membrane per unit area and unit time when differentialpressure of 0.1 MPa is applied between membranes at the ambienttemperature of 25° C.

If the carbon dioxide gas permeating amount is high in case of themembrane used for dissolving carbon dioxide gas conventionally, thevapor permeating amount is also high. Thus, if drain is discharged outof the membrane module frequently, the dissolving efficiency of carbondioxide gas cannot be maintained, and particularly in case of hot water,this problem is remarkable.

The configuration of the membrane is not restricted to any particularone but it may be formed into a desired configuration, for example,hollow yarn membrane configuration, flat membrane configuration andother configurations as required. However, the hollow yarn membraneconfiguration is preferable because the membrane area per volume of themodule can be increased when it is processed to the module.

Although the membrane can be formed of only the nonporous membrane forthe reason for the stiffness and thickness of the material of the gaspermeation membrane, if the membrane thickness is minute or it is, forexample, of flat membrane in order to protect the membrane surface, itis permissible to use a reinforcement porous substance as a spacer. Ifit is formed of the hollow yarn membrane, it is possible to form to amulti-layer membrane by providing a supporting layer for supporting thehollow yarn membrane on the inner surface and/or the outer surface.These methods may be selected appropriately.

FIG. 5 shows an example of the desirable configuration of the membraneused for the present invention, which is a composite hollow yarnmembrane 21 comprised of three layers while having porous layers 21 b onboth sides of a nonporous layer 21 a. Because in such a composite hollowyarn membrane 21, both faces of the gas permeating nonporous membrane 21a are protected by the porous membrane 21 b, the nonporous layer is notdirectly touched at the time of processing or handling for actual usage,so as to protect the membrane from damage or contamination and further,the obtained hollow yarn membrane has an excellent mechanical strengthalso.

Examples of a gas permeating nonporous membrane material include anonporous membrane composed of segmented polyurethane or polymer blendof styrene base thermoplastic elastomer and polyolefin. Morespecifically, (S)-(EB)-(S) tri-block copolymer composed of copolymer(EB) produced by styrene base thermoplastic elastomer's hydrogenatingstyrene copolymer (S) and butadiene copolymer, nonporous membrane, whichis (S)-(BU)-(S) tri-block copolymer composed of styrene copolymer (S)and butadiene copolymer (BU), polymer produced by hydrogenating randomcopolymer composed of styrene monomer and butadiene monomer, randomcopolymer composed of styrene monomer and butadiene monomer and the likecan be mentioned.

As for the composition ratio of styrene base thermoplastic elastomer andpolyolefin, it is preferable that styrene base thermoplastic elastomeris 20 to 95 mass portion and polyolefin is 80 to 5 mass portion withrespect to 100 mass portion which is total of both the compositions andmore preferably, the styrene base thermoplastic elastomer is 40 to 90mass portion while the polyolefin is 60 to 10 mass portion.

When the composite hollow yarn membrane is used, as a polymer materialwhich constitutes a porous layer, it is permissible to use polyethylene,polypropylene, polyolefin base polymer such as poly(3-methylebutene-1)and poly(4-methylpentene-1), polyvinylidene fluoride, fluoro basepolymer such as polytetrafluorethylene, polystyrene, and polymer such aspolyether ether keton and polyether keton.

As regards the membrane forming method, an appropriate known membraneforming method may be selected depending on the formability, moldabilityand the like of the material. If taking an example of forming a hollowyarn membrane configuration, a material of a carbon dioxide gas addingmembrane is extruded in a molten state from a hollow pipe sleeve andafter cooling, wound up according to a conventionally well known method.

To dissolve carbon dioxide gas into water, water is fed to one surfaceof the gas permeation membrane and carbon dioxide gas is applied with apressure to the other surface thereof. If the hollow yarn membrane isused, it is permissible to adopt a method in which water is fed into thehollow portion in the hollow yarn membrane while carbon dioxide gas isapplied to the outside of the hollow yarn membrane (hereinafter calledinternal circulation method) or it is permissible to adopt a method inwhich liquid is fed outside the hollow yarn membrane while carbondioxide gas is applied to the hollow portion (hereinafter, calledexternal circulation method). Any one of these methods may be used.

If the hollow yarn membrane module 20 having the structure shown in FIG.4 is used, in case of the internal circulation method, water is suppliedto the hollow portion in the hollow yarn membrane 21 from the intake 24and further, carbon dioxide gas is supplied under an appropriatepressure to the outside of the hollow yarn membrane 21 from the intake26. Consequently, water in which carbon dioxide gas is dissolved can beobtained from the outlet 25. The outlet 27 is usually closed at thistime and opened as a drain discharge port if necessary to dischargewater which permeates as vapor.

In case of the external circulation method, carbon dioxide gas issupplied into the hollow portion in the hollow yarn membrane 21 from theintake 24 and water is supplied to the outside of the hollow yarnmembrane 21 from the intake 26 and then, water in which carbon dioxidegas is dissolved is obtained from the outlet 27. At this time, usually,the outlet 25 is closed and then opened as a drain discharge portappropriately to discharge water which permeates as vapor.

The drain discharge port is preferred to be disposed at a position whichallows drain collected in a space on the side of the carbon dioxide gasin the hollow yarn membrane module to be discharge without any remainingand provided at a position located on the bottom when a module isprovided.

In some case, the drain discharge port is provided with anopening/closing valve which is closed when carbon dioxide gas is addedand opened/closed manually as required. In other case, it is providedwith an electromagnetic valve, which is opened or closed every specifiedtime or may be automatically opened when a predetermined amount of drainis collected by a water level sensor or the like which is installed in aspace on the gas side.

As for the discharge of drain, after the supply of carbon dioxide gas isstopped, water can be discharged using a remaining pressure of carbondioxide gas remaining in the membrane module. If the drain is dischargedtoo frequently at this time, the amount of carbon dioxide which isdischarged out of the module together with the drain and consumedwithout being dissolved in water is increased. Thus, it is economicallyimportant to use a membrane having a low vapor permeability to avoid thedrain discharge if possible.

Particularly, in case of the external circulation method, drain iscollected inside the hollow yarn membrane and the volume in which drainis deposited is smaller than the internal circulation method. Thus, thepermeating vapor amount is small and therefore, using a membranegenerating not so much drain is very effective.

Preferably, the membrane density inside the carbon dioxide gas addingmembrane module is set in a range of 2000 to 7000 m²/m³ in order toallow carbon dioxide gas or water contact the membrane surfaceeffectively and keep water feeding pressure loss in an appropriaterange.

Further, the internal circulation method has such an effect that drainis moved to the bottom of the module without any remaining by its weightand discharged in a short time in addition to an effect that carbondioxide gas can be dissolved efficiently by keeping the membrane densityin this range.

More preferably, the membrane density is in a range of 4000 to 6000m²/m³.

The membrane density of the membrane module refers to a value obtainedby dividing the membrane area of the membrane module by the volume ofthe membrane module. In the meantime, the membrane area of the membranemodule refers to the total area of the membrane surface, which is alarger one of the side in contact with liquid or the side in which gasis supplied. In case of the composite hollow yarn membrane having threelayers in which the porous layers are disposed on both sides of theaforementioned nonporous layer, it refers to a sum of the outsidesurface area of the porous layer.

The volume of the membrane module refers to the volume of a space inwhich the hollow yarn membrane 21 is disposed excluding connectionportions for suction or liquid feeding in case of the membrane moduleintegrated with the housing 20. In case of a type which is accommodatedin a cylindrical housing 20l having plural slits like an ordinary10-inch cartridge, it refers to the volume of a space in which thehollow yarn membrane 21 is disposed within the cylindrical housing.

It is described that there exists a blood flow rate increase effect whencarbon dioxide gas concentration exceeds about 300 mg/l as described in“The effects of external CO₂ application on human skin microcirculationinvestigated by laser Doppler flowmetry. Int J Microcirc: Clin Exp4:343–350 (1985)” and the carbon dioxide gas concentration is preferredto be 300 mg/l or more.

On the other hand, the saturated solubility of carbon dioxide gas at 40°C. is about 1300 mg/l, and even if more carbon dioxide gas than thisconcentration is added, the dissolving efficiency drops so thatundissolved gas is spouted from the outlet together with water, which isnot preferable.

As for the method for adjusting a carbon dioxide gas concentration, itcan be adjusted easily by adjusting the supply pressure of carbondioxide gas with such a pressure adjusting unit as a regulator.

If water temperature is raised after gas is added, dissolved gas returnsto bubbles so that the gas concentration in water drops, which is notpreferable. Thus, the temperature of water flowing through the waterpath is preferred to be adjusted in a range of 30° C. to 50° C.

If the water temperature is 30° C. or higher, generally, discomfort isnot felt when the skin makes contact with the water in foot bathing ortaking shower. If water is not used just after carbon dioxide gas isadded, it is permissible to add carbon dioxide gas at temperatures about50° C. and adjust the water temperature to a suitable one by allowing itto cool. A preferable temperature range is from 35° C. which is atemperature around the human temperature to 40° C.

Because the vapor permeating amount increases as the temperatureincreases, the carbon dioxide gas adding module of the present inventioncan be used preferably when carbon dioxide gas is dissolved into hotwater.

The diameter of an opening in the surface of the porous substance ispreferred to be 0.01 to 10 μm in order to control the flow rate ofdiffused carbon dioxide gas and form minute bubbles. If the holediameter exceeds 10 μm, bubbles rising in water become too large,thereby the dissolving efficiency of carbon dioxide gas being likely todrop. Further, if it is less than 0.01 μm, the diffused amount in waterdecreases so that carbonated spring having a high concentration islikely to be impossible to obtain.

The porous substance disposed in the diffusing portion of the diffusingmeans is capable of generating more bubbles as the surface area thereofis larger, so that contact between carbon dioxide gas and hot water isprogressed efficiently and further, dissolving before generation of thebubbles is progressed, thereby intensifying the dissolving efficiency.Therefore, although the configuration of the porous substance is notrestricted to any particular one, it is more preferable as the surfacearea is larger. Although as means for enlarging the surface area, thereare various methods, for example, a method of forming the poroussubstance cylindrically and a method of forming a flat shape andproviding its surface with unevenness, it is preferable to use theporous hollow yarn membrane and particularly, using a bundle of multipleporous hollow yarn membranes is effective.

As the material of the porous substance, various kinds of materials,such as metal, ceramic and plastic can be mentioned. Hydrophilicmaterial is not preferable because hot water invades into the diffusingmeans through pores in the surface when the supply of carbon dioxide gasis stopped.

Although the temperature of hot water for use is not restricted,preferably, it is from 30 to 45° C. and more preferably, it is 35 to 40°C. because the highest heat insulation effect is secured.

Some types of instruments for measuring the concentration of carbondioxide gas dissolved in water have been well known. A circulation typecarbon dioxide gas concentration meter comprises a carbon dioxide gaselectrode and a carbon dioxide gas concentration indicator. Electrodemembrane and internal liquid need to be replaced every one to threemonths, so that its maintenance takes time and labor and the cost ishigh. Further, because it is disadvantageous for measurement of a highconcentration, it lacks practical performance as a measuring instrumentfor use in the device for manufacturing carbonated spring.

A thermal conductivity detection type carbon dioxide gas concentrationmeter used in a carbonic beverage manufacturing device is very expensiveand not suitable for measurement of the concentration of carbonatedspring. As a low cost method, there is a method of calculating accordingto alkaline degree and pH of raw water used for carbonated spring.Carbon dioxide gas concentration in carbonated spring and pH ofcarbonated spring have a specified relation and the relation between thecarbon dioxide gas concentration and pH of carbonated spring changesdepending on the alkaline degree of raw water. Thus, to obtain thecarbonic acid concentration from pH, the alkaline degree of the rawwater needs to be measured. However, if this is obtained, the carbondioxide gas concentration can be measured easily from pH. Generally, therelation among alkaline degree, pH and carbon dioxide gas concentrationis established by a following Tillman's expression.Carbon dioxide gas concentration (mg/l)=10^(log[alkaline degree (CaCO) ₃mg/l)]+6.31−pH

Generally, the alkaline degree of raw water is not changed so much witha time passage if that is water obtained from a certain water sourcesuch as tap water. Thus, if a carbonated spring manufacturing device isinstalled and the alkaline degree of raw water is measured before thisis started, the value can be used after that. Of course, the alkalinedegree of raw water may be obtained each time when the carbonated springmanufacturing device is used. In the meantime, the alkaline degreementioned here is a way for indicating the amount of content ofcomponent which consumes acid such as OH, CO₃ ²⁻, HCO₃ and the likecontained in raw water and it is preferable to adopt pH4.8 alkalinedegree (M alkaline degree). For this method, pH needs to be analyzed ata high precision and its error needs to be suppressed within ±0.5 andmore preferably, within ±0.01. Therefore, it is preferable to calibrateperiodically, preferably each day of usage.

As another style of the carbon dioxide gas dissolver, a static mixer canbe mentioned. The static mixer is for separating fluid mechanically todiffuse carbon dioxide gas and not clogged in terms of its structureeven if a foreign matter is mixed in fluid so that it can be used forlong hours. The detail of the static mixer is described in Chapter 1 of,for example, Basic and Application of Static Mixer, supervised by ShingoHagiwara, issued by Nikkan Kogyo Shinbunsha (first edition is publishedSep. 30, 1981).

Although the solubility of carbon dioxide gas differs depending on theperformance of the dissolver, in case of circulation type, it isdetermined depending on the supply velocity of water supplied to thecarbon dioxide gas dissolver, namely, the ratio between the flow rate ofthe circulation pump and the supply velocity of carbon dioxide gassupplied to the dissolver. The lower the ratio between the carbondioxide gas supply velocity and water supply velocity, the higher thesolubility is. If the water supply velocity is constant, the carbondioxide gas supply velocity needs to be reduced to reduce the ratiobetween the carbon dioxide gas supply velocity and the water supplyvelocity. In this case, there is a disadvantage that manufacturing timeis prolonged. However, the relation between the ratio between the carbondioxide gas supply velocity and water supply velocity and the solubilitydiffers depending on the concentration of carbon dioxide gas in watercirculated to the dissolver. As the concentration is lower, thesolubility keeps excellent even if the ratio between the carbon dioxidegas supply velocity and water supply velocity is low and as theconcentration is increased, the solubility drops unless the ratiobetween the carbon dioxide gas supply velocity and water supply velocityis increased. According to a prior art, carbon dioxide gas is suppliedat the same supply velocity from a manufacturing startup to the endthereof without considering such a matter and by changing the carbondioxide gas supply velocity halfway, carbonated spring can bemanufactured at an excellent solubility.

For example, the carbon dioxide gas supply velocity at a startup ofmanufacturing is increased and when 10 to 50% the manufacturing time ispassed, the supply velocity of the carbon dioxide gas is reduce to about½ to 1/10. By executing this operation, it is possible to improved thesolubility and reduce the consumption of the carbon dioxide gas withoutprolonging the manufacturing time. This is just an example and thecarbon dioxide gas supply velocity can be changed through multi-stages.

To change the carbon dioxide gas supply velocity halfway in this way,plural carbon dioxide gas supply velocity means are provided in parallelas shown in FIG. 2 and in front half of the manufacturing time, anelectromagnetic valve 4′ for which the carbon dioxide gas supplyvelocity is set fast by the flow control valve 5 is opened in order toaccelerate the carbon dioxide gas supply velocity while the other valveis closed. In rear half of the manufacturing time, an electromagneticvalve 4′ for which the carbon dioxide gas supply velocity is set slow isopened in order to retard the carbon dioxide gas supply velocity whilethe other valve is closed. Although two flow control valves 5 are usedhere, it is permissible to control with three or more flow controlvalves.

In this indicated example, the circulation pump 9 is necessary formanufacturing carbonated spring in the circulation system. As the pump,a volume type proportioning pump having a self suction performance ispreferable. Using this enables stabilized circulation and alwaysconstant circulating water quantity to be achieved. Although if thecarbonated spring is dense, bubbles are more likely to occur so that abubble rich state is generated, even in this case, stabilized waterfeeding is achieved if a pump having self suction performance which canbe started without priming at the initial operation time is used.

In case where artificial carbonated spring is manufactured continuously,the artificial carbonated spring having a predetermined carbon dioxidegas concentration can be manufactured by combining the means formeasuring the carbon dioxide gas concentration and the method ofmanufacturing the artificial carbonated spring. As the method formeasuring the concentration of carbon dioxide gas in water, measurementbased on the ion electrode system is a general method. However,measurement in line and on time is impossible because it takes a longtime until the ion electrode is balanced in a solution having a highconcentration required by the artificial carbonated spring and anaccurate measurement is impossible as gas bubbles adhere to the ionelectrode.

Hereinafter, a carbonated spring continuous manufacturing deviceequipped with the carbon dioxide gas concentration measuring device of atypical embodiment of the present invention will be described withreference to the accompanying drawings. According to this embodiment,the example of the artificial carbonated spring will be described. Thegas concentration measuring method and gas dissolved solutionmanufacturing device of the present invention are not restricted to theartificial carbonated spring but may be applied to gas concentrationmeasurement of any solution obtained by dissolving gas regardless of thekind of the gas.

FIG. 6 is a diagram showing a configuration of the artificial carbonatedspring manufacturing device of the present invention.

As shown in the same figure, a take-in pipe A and a return pipe B forcirculating hot water 12 (after carbon dioxide gas is dissolved, turnsto artificial carbonated spring) loaded in the bath 11 as a storage bathfor the artificial carbonated spring communicate with the inside of thebath. Part of the return pipe B is constituted as a take-out pipe 15from the carbon dioxide gas dissolver 7. The hot water 12 in the bath 11is pumped up through the take-in pipe A by the suction pump 9 and apredetermined amount of the hot water 12 is introduced into the carbondioxide gas dissolver 7 as a gas dissolver through solution flow rateadjusting means 14.

Carbon dioxide gas supplied from the carbon dioxide gas cylinder 1 isadjusted in pressure by the pressure adjusting means 3 and the carbondioxide gas discharged from the pressure adjusting means 3 is adjustedin terms of the flow rate by the gas flow rate adjusting means 5 andthen introduced into the carbon dioxide gas dissolver 7. Detectionvalues detected by the pressure gauges 2 provided before and after thepressure adjusting means 3 are inputted to the control device 16 andthen, the pressure adjusting means 3 is controlled by a control signalfrom the same control device 16 so as to adjust the pressure of thecarbon dioxide gas.

Artificial carbonated spring discharged from the carbon dioxide gasdissolver 7 through the take-out pipe 15 and containing bubbles issubjected to measurement about the quantity of bubbles of carbon dioxidegas in the take-out pipe 15 by a measuring device 13 and returned intothe bath 11 through the artificial carbonated spring discharge port 10.

The measuring device 13 is provided with an ultrasonic wave transmitterand an ultrasonic wave receiver disposed across the take-out pipe 15 andultrasonic wave dispatched from the ultrasonic wave transmitter isreceived by the ultrasonic wave receiver so as to measure the strengthof the received ultrasonic wave. A measurement value obtained by themeasuring device 13 is inputted to the control device 16.

The control device 16 computes the carbon dioxide gas concentration inthe artificial carbonated spring discharged into the take-out pipe 15according to a relational expression between the quantity of bubbles incarbon dioxide gas preliminarily measured (damping rate of ultrasonicwave received by ultrasonic wave receiver=(strength of ultrasonic wavesignal received by ultrasonic wave receiver)/(strength of ultrasonicwave signal dispatched from ultrasonic wave transmitter): measured interms of %) and a measured value of the carbon dioxide gas concentrationin the artificial carbonated spring discharged from the carbon dioxidegas dissolver 7, corresponding to the flow rate of the hot water 12introduced into the carbon dioxide gas dissolver 7 and the introductionamount of carbon dioxide gas.

Corresponding to the carbon dioxide gas concentration of the artificialcarbonated spring by the control device 16, the solution flow rateadjusting means 14, the suction pump 9, the gas flow rate adjustingmeans 5 and the pressure adjusting means 3 are controlled so as toadjust the carbon dioxide gas concentration of the artificial carbonatedspring discharged from the carbon dioxide gas dissolver 7. When thecarbon dioxide gas concentration of the same artificial carbonatedspring reaches a desired carbon dioxide gas concentration, the suctionpump 9 and the pressure adjusting means 3 are controlled to endintroduction of the hot water 12 and carbon dioxide gas into the carbondioxide gas dissolver 7.

Instead of using the carbon dioxide gas cylinder 1, it is permissible touse carbon dioxide gas obtained by condensing carbon dioxide gas incombustion gas from combustion in a combustion device. In this case, theconcentration of the condensed carbon dioxide gas needs to be keptconstant.

As the pressure control means 3, a pressure control valve or the likemay be used. As the gas flow rate adjusting means 5 and the solutionflow rate adjusting means 14, a flow rate adjusting valve or the likemay be used. As the gas dissolver 7, a well known gas dissolver may beused and using the static mixer or hollow yarn membrane type dissolverenables the solubility of the dissolver to be intensified. Further, itis permissible to provide a pressure adjusting means in the downstreamof the suction pump 9 of the take-in pipe A and pressure gauges beforeand after the same pressure adjusting means to control the pressureadjusting means by the control device 16 according to detection valuesfrom the same pressure gauges.

It is permissible to provide the bath 11 with a faucet (not shown) topour hot water additionally or provide with a combustion device for hotwater to warm up the hot water. Although FIG. 6 shows the configurationfor circulating the hot water 12 to the carbon dioxide gas dissolver 7,it is possible to manufacture artificial carbonated spring by supplyinghot water from a hot water supply source (not shown) to the carbondioxide gas dissolver 7. It is permissible to arrange the carbon dioxidegas dissolvers in multi-stages in series to manufacture the artificialcarbonated spring. In these cases, by disposing a measuring device onthe take-out pipe from the carbon dioxide gas dissolver, the carbondioxide gas concentration of the artificial carbonated spring dischargedfrom the respective carbon dioxide gas dissolvers can be measured.

FIG. 7 is a diagram showing the relational expression between thedamping rate of the ultrasonic wave signal received by the ultrasonicwave receiver contained in the measuring device 13 and the measurementvalue of the carbon dioxide gas concentration of the artificialcarbonated spring flowing through the take-in pipe A. The samerelational expression is obtained under a condition that the flow rateof carbon dioxide gas introduced into the carbon dioxide gas dissolver 7and the flow rate of hot water are constant. Because the dissolvingcondition changes depending on the pressure of carbon dioxide gasintroduced into the carbon dioxide gas dissolver 7, the pressure of hotwater, dissolving capacity of the carbon dioxide gas dissolver,temperature and pressure at the time of dissolving within the carbondioxide gas dissolver 7 and the like, it is desirable to set up thecondition for manufacturing the artificial carbonated springpreliminarily with the gas dissolver 7 and obtain the aforementionedrelational expression under the set condition.

In the meantime, the present invention may be applied to manufacturingother than that of the artificial carbonated spring and in this case, itis necessary to obtain a relational expression between the quantity ofbubbles and gas concentration by measuring under the manufacturingcondition corresponding to the condition for manufacturing a solution.

As evident from FIG. 7, with a rise of the carbon dioxide gasconcentration of the artificial carbonated spring introduced to thecarbon dioxide gas dissolver (the carbon dioxide gas concentration ofthe artificial carbonated spring taken out of the carbon dioxide gasdissolver rises correspondingly because the dissolving condition in thedissolver is constant), the mixing amount (that is, quantity of bubbles)of undissolved gas in the artificial carbonated spring increases, sothat the ultrasonic wave signal dispatched from the ultrasonic wavetransmitter is damped and received by the ultrasonic wave receiver. Afollowing will be described again and to mix the non-dissolved gas intothe artificial carbonated spring, the carbon dioxide gas needs to beintroduced by a flow rate not less than the maximum dissolving amount bythe carbon dioxide gas dissolver 7.

The reception signal by the ultrasonic wave transmitter incorporated inthe measuring device 13 is subjected to the signal processing shown inFIG. 8. That is, after a signal received by the ultrasonic wave receiveris amplified and smoothed, signal values after a predetermined timeinterval are integrated and then, a value obtained by the integration(handled as a voltage value) is compared with a preliminarily setvoltage value. By this comparison, it can be detected that the dampingrate of the ultrasonic wave signal is a set value or less, or the carbondioxide gas concentration of the artificial carbonated spring is adesired carbon dioxide gas concentration or more.

Although the carbon dioxide gas concentration in hot water rises with apassage of the circulation time, artificial carbonated spring having adesired carbon dioxide gas concentration can be always obtained bycontrolling the ON/OFF of the suction pump 9 according to the detectionsignal from the measuring device 13. Further, by pouring hot waterdirectly from a supply unit such as a faucet into the bath to change theratio between the quantity of hot water of the artificial carbonatedspring and the supply amount of the carbon dioxide gas according to thedetection signal of the measuring device 13, the artificial carbonatedspring having a desired carbon dioxide gas concentration can beproduced.

EXAMPLES

Hereinafter, the present invention having the diversified embodimentswill be described more specifically with reference to the examples.

First, an example of the carbon dioxide gas adding membrane moduleapplied to the device of the present invention will be describedspecifically.

(Experiment No. 1)

With polymer blend composed of styrene base thermoplastic elastomer andpolypropylene (made by DAI-NIPPON PLASTICS Co., Ltd., product name MKresin MK-2F (Tg=−35° C., composition ratio: (S)-(EB)-(S) tri-blockcopolymer 50 mass portion, composed of polymer (EB) obtained byhydrogenating styrene polymer (S) and butadiene polymer, as styrene basethermoplastic elastomer and atactic polypropylene 50 mass portion aspolyolefin) as a material for a nonporous layer and polyethylene (madeby TOSOH CORPORATION, product name: NIPORON HARD 5110) as a material fora porous layer, a three-layered composite hollow yarn membrane shown inFIG. 5 having the outside diameter of 300 μm, the inside diameter of 180μm and the nonporous layer thickness of 2 μm was manufactured.

The carbon dioxide gas permeating amount of this composite hollow yarnmembrane was 3.3×10⁻² m³/m²·hr·0.1 MPa and the vapor permeating amountwas 22 g/m²·hr·0.1 MPa.

The carbon dioxide gas adding hollow yarn membrane module shown in FIG.4 was produced using the obtained composite hollow yarn membrane suchthat the hollow yarn membrane area was 0.71 m², the volume was 1.6×10⁻⁴m³ and the membrane density was 4438 m²/m³. An intermittent operation ofsupplying water of 40° C. by a flow rate of 5 l/min to the hollowportion in the hollow yarn membrane for three minutes while supplyingcarbon dioxide gas with a pressure of 0.36 MPa at 1.25 l/min and theninterrupting the supplies of carbon dioxide gas and water for 57minutes, which is a cycle of an hour was carried out continuously for1000 hours.

When 20% the effective length of the hollow yarn membrane was submergedin water, the drain discharge port was opened for first one minute of57-minute stop time to discharge drain using remaining carbon dioxidegas pressure. All drain in the module was discharged in the open time ofa minute.

Table 1 shows the generation amount per unit time of drain permeated tothe carbon dioxide gas supply side, the frequency of drain discharge andthe use amount of carbon dioxide gas.

(Experiment No. 2)

With thermoplastic segmented polyurethane (made by Thermedics Inc.product name; Tecoflex EG80A) as the material of the nonporous layer andpolyethylene (made by Tosoh Corporation, product name: Niporon Hard5110) as the material of the porous layer, the three-layered compositehollow yarn membrane shown in FIG. 5 having the outside diameter of 300μm, the inside diameter of 180 μm and the nonporous layer thickness of15 μm was produced.

The carbon dioxide gas permeating amount of the obtained compositehollow yarn membrane was 1.6×10⁻² m³/m²·hr·0.1 MPa and the vaporpermeating amount was 4.23×10² g/m²·hr·0.1 MPa.

The same carbon dioxide gas adding hollow yarn membrane as ExperimentNo. 1 was produced using this membrane and the same operation asExperiment No. 1 was carried out.

Table 1 shows the generation amount per unit time of drain permeatingthe carbon dioxide gas supply side, the frequency of drain discharge andthe use amount of carbon dioxide gas.

(Experiment No. 3)

A composite hollow yarn membrane having the same three-layered structureas Experiment No. 2 except that the thickness of the nonporous layer was1 μm was produced.

The carbon dioxide gas permeating amount of the obtained compositehollow yarn membrane was 2.6×10⁻¹ m³/m²·hr·0.1 MPa and the vaporpermeating amount was 6.8×10³ g/m²·hr·0.1 MPa.

The same carbon dioxide gas adding hollow yarn membrane module asExperiment No. 1 was produced using this membrane and the same operationas Experiment No. 1 was carried out.

Table 1 shows the generation amount per unit time of drain permeating tothe carbon dioxide gas supply side, the frequency of drain discharge andthe use amount of carbon dioxide gas.

TABLE 1 Drain discharge Carbon dioxide Drain amount frequency gas useamount ml/min Time/1000 hr kg/1000 hr Experiment No. 1 0.003 12 7.5Experiment No. 2 0.08 320 7.9 Experiment No. 2 0.77 3000 10.5

By using the carbon dioxide gas adding membrane module of the presentinvention as shown in Table 1, the consumption of carbon dioxide gascould be reduced.

The carbon dioxide gas adding membrane module of the present inventionenables carbon dioxide gas to be added into water even when hot water isfed because a membrane whose carbon dioxide gas permeating amount at 25°C. was 1×10⁻³ to 1 m³/m²·hr·0.1 MPa and whose vapor permeating amount at25° C. was 1×10³ g/m²·hr·0.1 MPa or less was used. Because the amount ofvapor permeating the membrane is small and drain is unlikely to bedeposited on the gas side, the frequency of drain discharges and theamount of carbon dioxide gas discharge into the atmosphere at the timeof drain discharge can be reduced. Accordingly, the carbon gas additivewater can be obtained at a high efficiency for a long time, so that themodule can be applied widely to applications for adding carbon dioxidegas to low temperature water, normal temperature water and further hightemperature water.

Further, because the membrane density of the carbon dioxide gas addingmodule is in a range of 2000 to 7000 m²/m³, drain can be dischargedsmoothly while maintaining the dissolving efficiency of the carbondioxide gas high.

If carbon dioxide gas is dissolved after water is heated to 30° C. to50° C. preliminarily, carbon dioxide gas can be dissolved efficiently.

Next, a typical embodiment of the carbonated spring manufacturing deviceof the present invention will be described. The carbon dioxide gasconcentration of the carbonated spring was obtained according toTillman's expression by measuring alkaline degree and pH.

(Experiment No. 4)

Carbonated spring was produced with the circulation type device shown inFIG. 1. The carbon dioxide gas pressure was controlled to 0.4 MPa with apressure control valve. As a flow meter, an electronic mass flow meter(CMS0020) made by Yamatake Hanewel Co., Ltd. was used and as a flowcontrol valve, a mass flow control valve (MODEL 2203) made by KOFLOK K.K. was used to control the carbon dioxide gas flow rate to 1.0 l/min(converted under 20° C.). As a dissolver, non-used hollow yarn moduleproduct made with a three-layered composite hollow yarn membrane (madeby Mitsubishi Rayon Co., Ltd.) whose membrane area was 0.6 m² was used.Hot water at 40° C. was poured into the bath by 10 l and the hot waterwas returned to the bath by 5 l every minute by means of a suction pump.

Table 2 shows the result obtained 10 minutes after circulation. Thefirst time in Table 2 indicates the result collected first in theexperiment and the second time indicates the result collected after thefirst time. Both indicated the same carbon dioxide concentration.

(Experiment No. 5)

The flow control valve of Experiment No. 4 was released to control thecarbon dioxide gas supply amount with pressure. The pressure wascontrolled to 0.15 MPa. Table 2 shows the result thereof. The carbondioxide gas concentration was low at the first time and high at thesecond time.

TABLE 2 Carbon dioxide gas Frequency concentration (mg/l) Experiment No.4 First time 1310 Second time 1310 Experiment No. 5 First time 1040Second time 1230(Experiment No. 6)

This experiment was executed in the same manner as in Experiment No. 4except that the flow rate of the circulation pump was 1 l every minute,that is, the ratio between the flow rate of the circulation pump and theflow rate of the carbon dioxide gas was set to 1. At the first time, thecarbon dioxide gas concentration dropped to 700 mg/l, so that thedissolving efficiency was reduced remarkably.

(Experiment No. 7)

Carbonated spring was produced with the one-pass type device shown inFIG. 3. The carbon dioxide gas pressure was controlled to 0.4 MPa withthe pressure control valve. With the electronic mass flow meter CMS0020made by Yamatake Hanewel Co., Ltd. as a flow meter and the floatcontroller MODEL 2203 made by KOFLOK K. K. as a flow control valve, thecarbon dioxide gas flow rate was controlled to 5.0 l/min (convertedunder 25° C.)

A hollow yarn module produced with the three-layered composite hollowyarn membrane (made by Mitsubishi Rayon Co., Ltd.) whose membrane areawas 2.4 m² was used as a dissolver. Water at 40° was fed to thedissolver at 5 l/min. Table 3 shows the result thereof. Carbon dioxidegas concentration was stabilized about two minutes after water was fedfirst.

(Experiment No. 8)

The flow control valve of Experiment No. 7 was opened to control thecarbon dioxide gas supply amount with a pressure. The pressure wascontrolled to 0.28 MPa. Table 3 shows the result thereof. The carbondioxide gas concentration in the initial period of water feeding wasunstable as compared with Example 4, so that the carbon dioxide gasconcentration was not stabilized even if 10 minutes passed after waterwas fed first.

TABLE 3 Water feeding time 1 2 3 5 7 10 Experiment No. 7 1190 1210 12101210 1210 1210 Experiment No. 8 610 820 940 1100 1160 1200(Experiment No. 9)

The same operation as Experiment No. 4 was carried out with a moduleused for 500 hours and its result was compared with the result ofExperiment No. 4 using the unused product. Table 4 shows the resultthereof. The same performance as the unused product was obtained.

(Experiment No. 10)

The same operation as Experiment No. 5 was carried out with a moduleused for 500 hours and its result was compared with the result ofExperiment No. 5 using the unused product. Table 4 shows the resultthereof. The carbon dioxide gas concentration dropped as compared withthe unused product.

TABLE 4 Use time Carbon dioxide gas (min) concentration (mg/l)Experiment No. 4 0 1310 Experiment No. 9 500 1290 Experiment No. 5 01040 Experiment No. 10 500 980

Next, an example about the dissolving efficiency of carbon dioxide gaswill be described specifically. The carbon dioxide concentration incarbonated spring was obtained according to Tillman's expression bymeasuring alkaline degree and pH. Table 5 shows a summarized result.Meanwhile, the dissolving efficiency in Table 5 was obtained from“dissolving efficiency (%)=carbon dioxide gas dissolving amount incarbonated spring/amount of used carbon dioxide gas×100”.

(Experiment No. 11)

Carbonated spring was produced with the circulation type device shown inFIG. 2. The carbon dioxide gas pressure was controlled to 0.4 MPa withthe pressure control valve. Two mass flow control valves (MODEL 2203)made by KOFLOK K. K. were used as the flow control valves and the carbondioxide gas flow rate of one of them was adjusted to 2.0 l/min(converted under 20°) while the other was adjusted to 0.5 l/min(converted under 20°). As the dissolver, a hollow yarn module producedwith the three-layered composite hollow yarn membrane (made byMitsubishi Rayon Co., Ltd.) whose membrane area was 0.6 m² was used. Hotwater at 40° C. was poured into the bath up to 10 l and the hot waterwas returned to the bath by 5 l every minute by means of the circulationpump.

An electromagnetic valve was opened for carbon dioxide gas to flow tothe flow control valve adjusted to 2.0 l/min at the startup ofmanufacturing while the other valve was closed. Up to the end 2 minutesto 10 minutes after, the electromagnetic valve was opened for carbondioxide gas to flow to the flow control valve adjusted to 0.5 l/minwhile the other valve was closed. Table 5 shows its result.

(Experiment No. 12)

This experiment was carried out in the same manner as in Experiment No.11 except that the carbon dioxide gas was fed constantly at 1.0 l/min(converted under 20° C.) during manufacturing. Table 5 shows its result.The dissolving efficiency was lower than that of Experiment No. 11.

(Experiment No. 13)

This experiment was executed in the same manner as in Experiment No. 11except that carbon dioxide gas was fed constantly at 0.5 l/min(converted under 20° C.) during manufacturing. Table 5 shows its result.Although the dissolving efficiency was high, the carbon dioxide gasconcentration was lower than that of Experiment No. 11.

(Experiment No. 14)

This experiment was executed in the same manner as in Experiment No. 11except that carbon dioxide gas was fed constantly at 2.0 l/min(converted under 20°) during manufacturing. Table 5 shows its result.Although a high concentration carbonated spring could be obtained in ashort time, the dissolving efficiency was worsened remarkably.

TABLE 5 Carbon dioxide gas Dissolving Manufacturing concentrationefficiency time (min) (mg/l) (%) Experiment No. 11 10 1310 79 ExperimentNo. 12 10 1300 65 Experiment No. 13 10 1080 98 Experiment No. 14 8 132043

Finally, an example using the manufacturing device for the artificialcarbonated spring shown in FIG. 6 will be described specifically.

(Experiment No. 15)

Hot water at 40° C. was poured into the bath by 10 l and 20 l and thecirculation pump (5 l/min), a hollow yarn module produced with thethree-layered composite hollow yarn membrane (made by Mitsubishi RayonCo., Ltd.) whose membrane area was 0.6 m², a carbon dioxide gascylinder, a carbon dioxide gas flow control valve and a measuring devicefor detecting bubbles with ultrasonic wave were connected in the orderindicated in FIG. 6. The flow rate of carbon dioxide gas was set to 1.5l/min, the maximum value (when water is circulated) of a receptionsignal by the measuring device was set to 4.8 mV and the threshold of adetection signal dispatching was set to 3.1 mV (calculated from thedamping rate 65% which provides 1100 mg/l according to FIG. 7) and then,the circulation pump was operated. When the detection signal wasdispatched, the operation was stopped and the carbon dioxide gasconcentration of the produced artificial carbonated spring was measuredwith an ion electrode type carbon dioxide gas measuring device (made byToa Denpa: IM40).

As a result, artificial carbonated spring having a target carbon dioxidegas concentration of 1100 mg/l shown in Table 6 was obtained.

TABLE 6 Setting Measured value of Quantity of hot concentration (ppm)carbon dioxide gas water (1) Damping rate (%) concentration (ppm) 101100 1120  65% 20 1100 1100  65%Effect of the Invention

According to the carbonated spring manufacturing device of the presentinvention, which comprises a carbon dioxide gas dissolver and acirculation pump, water in a bath is circulated by the circulation pumpthrough the carbon dioxide gas dissolver and carbon dioxide gas issupplied into the carbon dioxide gas dissolver so as to dissolve carbondioxide gas into water. By raising the carbon dioxide gas concentrationin water gradually, carbonated spring having a high concentration ismanufactured. By retarding the supply velocity of the carbon dioxide gasin the latter half period as compared with the former half period of themanufacturing time, high concentration carbonated spring can be obtainedeffectively.

According to the carbonated spring manufacturing method of the presentinvention, carbon dioxide gas supplied from a carbon dioxide gascylinder is controlled in terms of the gas flow rate to allow it to flowinto the dissolver and dissolved into hot water. Consequently, acarbonated spring manufacturing method capable of obtaining anunchanging carbonic acid concentration can be provided.

According to the carbon dioxide gas adding membrane module of thepresent invention, because the carbon dioxide gas permeating amount andvapor permeating amount under a predetermined temperature are set in apredetermined range, carbon dioxide gas can be added into water evenwhen it is fed to hot water. Particularly, because the quantity of vaporpermeating the membrane is small and drain is unlikely to be depositedon the gas side, the frequency of drain discharges and the quantity ofcarbon dioxide to be discharged into the atmosphere at the time of draindischarge can be reduced. Further, because carbon dioxide gas addedwater can be obtained at a high efficiency in a long period, this modulecan be applied widely to applications for adding carbon dioxide gas tolow temperature water, normal temperature water and high temperaturewater.

Further, because the membrane density of the membrane module is set in arange of 2000 to 7000 m²/m³, drain can be discharged smoothly whilemaintaining the dissolving efficiency of carbon dioxide gas high. Whencarbon dioxide gas is dissolved after water is heated to 30° C. to 50°C. preliminarily, carbon dioxide gas can be dissolved effectively.

1. A device for manufacturing a gas dissolved solution for carbonatedspring, comprising: a carbon dioxide gas supply port; a carbon dioxidegas dissolver which communicates with the carbon dioxide gas supplyport; a water bath; a circulation pump for feeding water in the waterbath into the carbon dioxide gas dissolver and for returning into thewater bath; and further comprising plural carbon dioxide gas supplyvelocity control means capable of setting carbon dioxide gas supplyvelocities to different levels in parallel, and gas velocity changeovermeans for carbon dioxide gas supply velocity.
 2. The device formanufacturing a gas dissolved solution according to claim 1, wherein thegas velocity changeover means is an electromagnetic valve.
 3. The devicefor manufacturing a gas dissolved solution according to claim 1, whereineach of the carbon dioxide gas supply velocity control means is a flowcontrol valve.
 4. The device for manufacturing a gas dissolved solutionaccording to claim 3, wherein the flow control valve is a mass flow ratetype flow control valve.
 5. A method for manufacturing a gas dissolvedsolution for carbonated spring, wherein, when water in a water bath iscirculated by a circulation pump through a carbon dioxide gas dissolverwhile carbon dioxide gas is supplied into the carbon dioxide gasdissolver so as to dissolve carbon dioxide gas into the water in thewater bath to raise the carbon dioxide gas concentration of the water inthe water bath gradually, the carbon dioxide gas supply velocity isretarded in a latter period of the carbon dioxide gas dissolving time ascompared with the carbon dioxide gas supply velocity in an initialperiod of the gas dissolving time.
 6. The method for manufacturing a gasdissolved solution according to claim 5, wherein a period of time whenthe carbon dioxide gas supply velocity is retarded is the same or longerthan a period of time when the carbon dioxide gas supply velocity isexpedited.
 7. The method for manufacturing a gas dissolved solutionaccording to claim 5, wherein the carbon dioxide gas supply velocityjust before dissolving of carbon dioxide gas ends is 50% or less of thesupply velocity when dissolving of carbon dioxide gas starts.
 8. Themethod for manufacturing a gas dissolved solution according to claim 6,wherein the period of time when the carbon dioxide gas supply velocityis expedited is 10 to 50% of the carbon dioxide gas dissolving time.